Furnace electrode seal

ABSTRACT

An electric furnace seal including a first water cooled seal ring mounted on the furnace adjacent the electrode opening. A support ring is on the seal ring and the support ring is supported independently of the seal ring, yet engages a seal surface of the ring. A second seal ring is seated on the support ring and is constrained for transverse movement only and against upward movement relative to the support ring. The opening through the lower seal ring and the support ring is somewhat greater than the diameter of the electrode, whereas the opening through the second seal ring is of a diameter approximating that of the electrode. A frusto-conical packing retaining hat extends upwardly from the second seal ring and provides for packing the upper end of the slight clearance space between this seal ring and the electrode. By virtue of this arrangement where the second seal ring &#39;&#39;&#39;&#39;floats&#39;&#39;&#39;&#39; on the support ring, a good seal is maintained which prevents the escape of hot gases at the opening yet allows transverse movement of the electrode during lifting and lowering.

United States Patent 91 Beerman [54] FURNACE ELECTRODE SEAL [75] Inventor: Ludovicus Johannes Beerman, Tracy, Quebec, Canada [73] Assignee: Quebec Iron and Titanium Corporation, Sore], Quebec, Canada [22] Filed: Nov. 12, 1970 [21] Appl. No.: 88,550

[52] US. Cl. 0277/12, 13/17, 277/16, 277/30 [51] Int. Cl. ..Fl6j 15/56 [58] Field of Search ..277/l2, 16, 24, 30, 31, 97, 277/98,100,101, 220, 226; 13/14-17 Primary Examiner-Robert G. Nilson Attorney-John L. Sniado and Walter Kruger [57] ABSTRACT An electric furnace seal including a first water cooled seal ring mounted on the furnace adjacent the electrode opening. A support ring is on the seal ring and the support ring is supported independently of the seal ring, yet engages a seal surface of the ring. A second seal ring is seated on the support ring and is constrained for transverse movement only and against upward movement relative to the support ring. The opening through the lower seal ring and the support ring is somewhat greater than the diameter of the electrode, whereas the opening through the second seal ring is of a diameter approximating that of the electrode. A frusto-conical packing retaining hat extends upwardly from the second seal ring and provides for packing the upper end of the slight clearance space between this seal ring and the electrode. By virtue of this arrangement where the second seal ring floats on the support ring, a good seal is maintained which prevents the escape of hot gases at the opening yet allows transverse movement of the electrode during lifting and lowering.

18 Claims, 5 Drawing Figures FURNACE ELECTRODE SEAL This invention relates to an improved seal for an electric furnace of the type in which a large diameter electrode extends through an opening in the furnace to melt the contents of the furnace.

More particularly, the invention relates to a floating ring electrode seal for an electric furnace of the type in which the electrode is raised and lowered during operation of the furnace, so the electrode is maintained at a predetermined level relative to the molten metal in the furnace.

Electric arc furnaces are widely used for various metal smelting and refining operations. The typical furnace may include a plurality of graphite electrodes which extend through openings in the roof of the furnace to a location adjacent the level of the melt in the furnace. Typically, the furnace may include perhaps six 2-foot diameter electrodes.

As the refined metal is tapped from the furnace, a batch of ore, and/or metal, and/or a reducing agent, is added to the furnace. When molten metal is tapped from the furnace, the level within the furnace lowers and it is necessary to lower the electrodes to follow the level of the metal in the furnace. Then, when an additional charge is added to the furnace, the electrodes must be retracted to maintain them at the proper elevation relative to the metal in the furnace. As a result, the massive electrodes are frequently lowered and lifted to maintain proper operating conditions within the furnace. Typically, the electrodes are raised and lowered automatically by suitable controlled winches or other drive means which maintain the electrodes at the proper elevation relative to the material in the furnace.

To avoid the escape of hot gases with the corresponding loss of heat and efficiency of the furnace, it is necessary to provide a good seal where each electrode extends through the roof of the furnace. Unless a reasonably gas tight seal is maintained, rapid erosion, including necking in of the electrode, occurs along that length of the electrode which extends through the furnace roof. Such erosion not only weakens the electrode, with the danger that the lower end of the electrode can break off, but also reduces the diameter of the electrode with the result that the current carrying capacity of the electrode is substantially reduced. In addition, the size of the opening between the electrode increases as the electrode erodes. Tests show that typical temperatures of gases flowing outwardly from the furnace through the annulus between the furnace roof opening and the electrode are on the order of 3,000F., and hence, the electrode can be damaged by the escaping hot gases.

If it were practical and possible to lower the electrode along a precise vertical axis and maintain the electrode precisely centered on the axis, the opening through the furnace roof could, of course, be made sufficiently close to the diameter of the electrode that there would be little, if any, gas loss through the opening. However, because of the large current carried by each electrode, and because of the vibration caused by the arc between the end of the electrode and the furnace melt, it is virtually impossible to provide a close fit without danger of damage to the electrode or the roof of the furnace through which the electrode extends. in addition, as a result of conditions within the furnace,

the axis of the electrode may tilt slightly which presents further problems with a close fit of the electrode in the opening.

As previously explained, the electrodes are frequently lifted and lowered during operation of the furnace. When the electrode is lowered, it is also subjected to slag splashing from the contents of the furnace. If a close fitting opening or seal is provided, slag on the outer surface of the electrode can damage the seal when the electrode is elevated during charging of the furnace. As is well known in the electric furnace art, as the lower end of the electrode erodes, additional sections of electrode are threaded into or onto the upper end of the electrode so the furnace can be operated continuously without stopping the furnace to change or repair the electrodes. Customarily, a

threaded socket or pin is formed on the upper end of the electrode, and a new electrode having a mating threaded section is screwed onto this upper end so the electrode can be fed continuously. Because of the massive size of the electrodes, a perfect cylindrical surface is rarely obtained at the joint between two electrodes. Instead, the axes of the two electrodes are not precisely aligned, but are frequently slightly off-center so a shoulder or ledge is present at the joint. This ledge or shoulder further complicates obtaining and maintaining a good seal where the electrode passes through the roof of the furnace.

By virtue of the improved electric furnace seal of this invention, problems encountered in the past are obviated. This is accomplished by providing a seal assembly in which a first stationary seal ring assembly extends radially outwardly of the furnace opening and has an inside diameter somewhat greater than the diameter of the electrode. A second movable seal ring assembly of an inside diameter only slightly greater than the outside diameter of the electrode extends aroundthe electrode and suitable packing or stuffing is placed between the electrode and second ring to provide a sliding fit. Advantageously, the packing or stuffing is flexible to provide for axial movement of the electrode through the second seal ring. An additional advantageous feature of the seal arrangement is the relatively low axial height of the seal ring which permits limited tilting and rocking of the electrode without danger of damage. The movable seal ring is so arranged relative to the first seal ring that the second ring is free to float radially on the stationary ring and correspondingly, the second ring follows the normal lateral or transverse movements of the electrode. Advantageously, the sealing surfaces of the movable and stationary seal rings are generally horizontal and are formed from metal to resist deterioration at the high temperatures encountered. While it is necessary to provide for some radial or transverse movement of the second seal ring relative to the first seal ring, the extent of such movement must temperatures encountered. In addition, a seal plate is interposed between the lower stationary seal ring and the upper movable seal ring. The upper seal ring seats on a seal surface of the seal plate which in turn seats on the seal surface of the lower ring. The upper seal ring is mounted on the seal plate for transverse movement, but against upward movement. The seal plate is so mounted by supports, independent of the furnace roof, that the seal plate can move slightly upwardly to absorb shock, but returns to its sealing position with the lower seal ring. Such provision for upward movement of the seal plate, independently of the lower seal ring, prevents damage to the furnace roof if the electrode jams as it is elevated.

correspondingly, an object of this invention is an improvement in electric arc furnaces, wherein a large diameter electrode extends through an opening in the furnace, the improvement comprising a unique floating ring electrode seal.

Another object is an improved electrode seal for an electric furnace in which one element of the seal closely embraces the electrode, yet permits passage of the electrode therethrough, and another larger diameter element of the seal presents an upwardly facing surface engageable with a downwardly facing surface of the seal element embracing the electrode.

Another object is a unique seal for the electrode of an electric arc furnace, the seal including an elongated high temperature packing receiving sleeve to facilitate packing the annulus between the electrode and the sleeve with a high temperature flexible insulation that allows relative axial and tilting movement between the seal and the electrode.

A further object is a seal for a furnace electrode in which a lower water cooled seal ring has a diameter substantially greater than the electrode and presents an upwardly facing seal surface, an upper water cooled seal ring has a downwardly facing seal surface which engages the upwardly facing surface, the upper seal ring closely embraces the electrode, a cone-shaped sleeve extends from the upper seal ring and diverges in a direction away from the ring, guides are provided between the sleeve and the electrode to guide the electrode through the upper ring, and flexible packing is supported in the sleeve, adjacent the guides, to prevent passage of hot gases between the electrode and the upper ring.

A still further object is a seal according to the preceding objects in which an intermediate seal plate is positioned between the sealing surfaces of the upper and lower seals, the upper seal is mounted on the seal plate for transverse movement, but against vertical movement, and the seal plate is mounted for slight upward movement independently of the furnace roof and lower seal.

Numerous other objects, advantages, and features of the invention will become apparent with reference to the drawings which form a part of this specification, and in which:

FIG. 1 is a fragmentary pictorial view showing the roof of an electric furnace with the seal arrangement of this invention mounted thereon;

FIG. 2 is a top view, in section, taken along line 2--2 of FIG. 1, and showing the seal arrangement of this invention in plan;

FIG. 3 is a plan view of the lower seal ring;

FIG. 4 is an enlarged view, in section, taken along line 4--4 of FIG. 2; and

FIG. 5 is a partial view, in section, showing the support arrangement for the seal assembly of this invention.

Referring now to the drawings in detail, and particularly to FIG. 1, there is shown a furnace roof 1 comprised of a refractory material including brick work 2 defining a circular opening 3 through which an electrode 4 extends from a location outside the furnace. Supported at the upper end of opening 3, and seated on the brick work 2 adjacent the opening, is a stationary seal assembly 5 which extends around the electrode and is concentric with the axis of opening 3. Seated on stationary seal assembly 5 is a movable seal assembly 6.

Stationary seal assembly 5 includes a lower gland or seal ring 7 and a support ring assembly 8 seated on the lower seal ring. Movable seal assembly 6 includes an upper seal ring 9, having a frusto-conical upwardly diverging hat 10 secured to the seal ring, to provide an annular space for a high temperature resistant flexible packing 12, such as asbestos, which seals the movable seal assembly 6 to electrode 4.

As shown at FIGS. 3 and 4, lower seal ring 7 is comprised of two substantially identical semi-circular segments l3 and 14. Segment 13 has an arcuate planar upwardly facing seal surface 15, and segment 14 has an arcuate planar upwardly facing seal surface 16. Advantageously, seal surfaces 15 and 16 lie in a common horizontal plane. Secured, as by welding, to each end of segment 13 is a connecting plate 17 which extends radially outwardly beyond seal surface 15. Similarly, a connecting plate 18 is secured, as by welding, to each end of segment 14. Connecting plates 17 and 18 lie flat against each other and bolts 19 passed through the connecting plates secure segments 13 and 14 together with surfaces 15 and 16 in a common horizontal plane. Advantageously, the upwardly facing edges of connecting plates 17 and 18 lie in a common plane with surfaces 15 and 16 to present a continuous annular seal surface 20 on lower seal ring 7.

As shown at FIGS. 2-4, segments 14 and 15 are hollow and have a flat top wall 21, a flat bottom wall 22 spaced vertically from top wall 21, an outer arcuate side wall 23 extending between and joining the top and bottom walls, and an arcuate inner side wall 24. Inner side wall 24 is axially elongated and extends a substantial distance below bottom surface 25 of bottom wall 22. The space between walls 2l-24 is divided by an arcuate upright baffle 26, which provides a flow passage for cooling water within each hollow segment.

As shown at FIG. 3, baffle 26 originates at a location between an inlet pipe 27 and an outlet pipe 28 on the outer side wall and extends arcuately to a location spaced from connecting plate 18. The baffle directs cooling water from inlet pipe 27, first along the inner side wall of the segment, and then back along the outer side wall to outlet pipe 28.

Secured to the outer surface 29 of outer side wall 23 are four support brackets 30-33. These brackets are spaced apart from each other and extend radially outwardly of lower seal ring 7. The support brackets provide for supporting lower seal ring 7 independently of the fragile brick work of the furnace roof.

At the upper end of opening 3 is an annular recess 35 (FIG. 4). Inner side wall 24 of lower ring 7 is so constructed that it extends downwardly into recess 35 and bottom surface 25 of lower wall 22 seats on top surface 36 of the brick work surrounding opening 3. Suitable packing or cement can be used to seal lower seal ring 7 at opening 3.

Support ring assembly 8 includes a flat annular seal plate or ring 40 and an upwardly extending cylindrical wall 41 secured to the plate. As shown at FIG. 4, wall 41 seats on the top surface 42 of the plate adjacent its outer edge and is secured to the plate by welding. As shown at FIG. 2, wall 41 is discontinuous and comprises a plurality of arcuate wall segments 43-46. Extending between segments 43-46 are arcuate connector plates 47-50, respectively, which extend over the outer surfaces of the segments, are secured to adjacent segments with bolts 51 and bridge the spaces between adjacent segments. As shown at FIG. 4, for connector plate 49, bottom edge 51 of each connector plate is spaced a substantial distance above top surface 42 of seal plate 40. It will be observed with reference to FIG. 2, that the spaces between wall segments 43-46 are 90 circumferentially from each other. Connector plates 47 and 49 are diametrically opposed from each other, and connector plates 48 and 50 are diametrically opposed and are spaced 90 from each of connector plates 47 and 49.

Secured to the outer surface of each wall segment 43-46 is a support bracket 55. As shown at FIGS. 2 and 5, each support bracket 55 includes a vertical leg which extends radially outwardly from the wall segment to which it is connected.

As shown at FIG. 2, upper seal ring 9 is diametrically split and is comprised of two identical semi-circular ring segments 56 and 57. The segments are secured together by bolts extending through end plates, in the form of arms 58, at each end of segment 56, which mate with arms 59 secured to each end of segment 57.

As shown at FIG. 4, segments 56 and 57 of upper seal ring 9 each have a horizontal top wall 61, a horizontal bottom wall 62 spaced from the top wall, an outer arcuate side wall 63 and an inner arcuate side wall 64. These walls cooperate with the respective connector plates 59 to form a cooling water passage 65 that extends from inlet pipe 66 to outlet pipe 67 for segment 57, and which extend from inlet pipe 68 to outlet pipe 69 for segment 56.

Secured to segment 57 is a radially extending restraining or positioning arm 70. Arm 70 is flat and elongated and has a top edge that extends horizontally in closely adjacent relation to bottom edge 51 of connector plate 49. The relationship between edge 51 and edge 71 is such that upper seal ring 9 can slide horizontally with its lower surface 72 in engagement with upper surface 42 of seal plate 40, but cannot move vertically upwardly relative to the plate. The same relationship exists between restraining arm 73 secured to segment 56 and connector plate 47 which extends between wall segments 43 and 44. Similarly, arms 58 and 59 extend under arcuate connector plate 50 at one side of upper seal ring 9, and the upwardly facing edges of arms 58 and 59 are closely adjacent the downwardly facing edge of connector plate 50. A similar relationship exists between arms 58 and 59 and connector plate 48 at the opposite side of upper seal ring 9. This arrangement provides for floating of upper seal ring 9 on surface 42 of seal plate 40, but prevents lifting of the ring from the surface 42. It will be noticed with reference to FIG. 2, that arm is diametrically opposite arm 73, and that these arms are spaced midway between arms 58, 59, so the several arms are spaced circumferentially of each other.

Mounted on the top surface of top wall 61 of upper seal ring 9 is the hat 10. The hat is mounted on wall 61 at a location adjacent its intersection with outer side wall 63, so wall 61 presents an upwardly facing transverse shoulder 76 within the confines of hat l0. Hat 10 is diametrically split in the vertical plane defined by the mating surfaces of arms 58 and 59, and correspondingly, the hat is formed from two semi-circular frusto-conical segments with their facing side edges closely adjacent each other. As previously explained, hat 10 diverges in an upward direction, and advantageously, the inside surface of hat 10 makes an angle of 15 with the axis of opening 3.

Mounted within the hat are six equally circumferentially spaced guide plates 77. As shown at FIG. 4, the lower edge of each guide plate seats on shoulder 76 and the outside edge 78 of each guide plate engages and is secured to the inside surface of hat 10, for example, by welding. Each guide plate 77 has an inwardly facing upwardly inclined guide edge 79 that joins transverse shoulder 76 at its inner edge. Edge 79 makes an angle of 15 with the axis of opening 3. As shown at FIGS. 2 and 4, each guide plate 77 is formed from angle stock to facilitate securing the guide plate to the inside of hat 10.

As shown at FIG. 4, the lower inside corner of upper seal ring 9 is beveled to provide a downwardly facing frusto-conical guide surface 81 that merges with inside surface 80. In addition, the outer circumferential edge 82 of bottom wall 62 of ring 9 is machined so it makes an angle of less than 90 with bottom surface 72. This provides a sharp corner which scrapes and cleans surface 42 as ring 9 moves during operation of the furnace.

ASSEMBLY First, segments 13 and 14 are bolted together to form lower seal ring 7. Next, this seal ring is mounted on the furnace roof with the lower portion of wall 24 extending into recess 35. Lower seal ring 7 may be sealed to the furnace roof with a suitable cement to prevent leakage between bottom surface 25 of the ring and top surface 36 of the brick work.

Next, support ring assembly 8 is placed on lower seal ring 7 with lower sea] surface 84 of seal plate 40 in engagement with upper surface 20 of the seal ring. Arcuate connector plates 47-50 are removed at this time to install movable seal assembly 6, which includes upper seal ring 9 and hat 10. Then, segments 56 and 57 of upper seal ring 9 are bolted together at arms 58 and 59 and the assembly is lowered onto seal plate 40 so lower surface 72 of the seal ring sits on surface 42 of seal plate 40. It will be observed with reference to FIG. 2, that support ring assembly 8 is so oriented that its support brackets 55 are vertically aligned with support brackets 30-33 of lower seal ring 7. In addition, upper seal ring 9 is so oriented circumferentially that restraining arms 70 and 73 extend through the relatively narrow spaces between wall segments 41 and 44, and wall segments 45 and 46 respectively, and that pipes 67 and 69 and 66 and 68 extend through the wider spaces between wall segments 44 and 45 and 43 and 46, respectively.

Next, connector plates 47-50 are bolted to the respective segments 43-46. Then, connections are made to the cooling water pipes 66-69 of the upper seal ring 9 and to pipes 27 and 28 of lower seal ring 7. Then, a tie rod 86 is secured between each support bracket 55 and support plates 87 which are secured at a location above the furnace roof, as shown at FIG. 5. Each tie rod 86 extends upwardly and outwardly from support bracket 55. Similarly, a tie rod 87 is secured to each of the support brackets 30 of lower seal ring 7 and the upper end of the tie rod is secured to a support plate 89 mounted at a location above the furnace roof. Tie rods 87 extend upwardly and outwardly of the respective connector brackets 30-33. The function of tie rods 87 is to partially support lower seal ring 7 independently of the fragile brick work of the furnace roof. These tie rods also prevent the lower seal ring from falling into the furnace where it could contaminate the contents of the furnace in the event that the furnace roof caves in adjacent opening 3. Tie rods 86 similarly partially support support ring assembly 8. The tie rods 86, however, are somewhat flexible and permit slight upward movement of support ring 8 relative to lower seal ring 7. By virtue of this flexible mounting, support ring 8 can move upwardly with upper seal ring 9 should the electrode jam when it is lifted. Since the tie rods 86 mount support ring 8 independently of the furnace roof, no stresses are imposed on the fragile roof, and damage is prevented.

After the several seal rings and support ring are mounted and tie rods 86 and 87 are connected, electrode 4 is lowered through the hat 10 and upper seal ring 9. Then, packing 12 is placed in hat 10 and is rammed or otherwise compressed so it engages electrode 4 and closes the upper end of the slight clearance space between the inner surface 80 of upper seal ring 9 and the outer surface of electrode 4.

OPERATION In operation of the furnace, the level of the melt within the furnace changes as molten material is tapped from the furnace and as new charges of material are added to the furnace. The position of the lower end of electrode 4, relative to the melt, is automatically controlled by a lifting and lowering device for the electrode (not shown) such as a winch which is controlled through a regulator in response to the voltage and current passed through the electrode. Since it is desirable to maintain power through the electrode constant, the winch lowers the electrode as material is tapped from the furnace, and raises the electrode as a charge is added to the furnace.

As is apparent with reference to FIG. 4, opening 3 through the furnace roof is somewhat larger than the diameter of electrode 4. When large diameter elec-v trodes are used, this opening may be as much as several inches greater than the diameter of the electrode. The opening 80 in the movable upper seal ring 9 is however, only slightly greater than the diameter of electrode 4. A clearance space of one-eighth inch between inner surface 80 and electrode 4 has been found to be extremely effective. Even with this relatively small clearance, the electrode can tilt relative to ring 9 because of the relatively small axial height of the inner surface of the ring. During such tilting, packing 12 gives so no excessive stresses are placed on either the electrode or seal ecause of the power consumed at the are at the lower end of electrode 4, the electrode vibrates laterally, as well as axially during its operation. Since the movable seal, including seal ring 9, is free to move transversely on surface 42 of seal plate 40, any transverse movement or vibration of the electrode is permitted by like movement of the seal ring along seal surface 42. When it is necessary to lower electrode 4, for example, when the furnace is tapped, guide plates 49 function to guide the electrode during its downward travel, and also function to maintain the packing l2 closely adjacent the sides of the electrode. When the electrode 4 is lifted, for example, when a charge is added to the furnace, the chamfered or beveled shoulder 81 at the lower edge of seal ring 9 functions to guide the electrode during such upward travel. If slag from the furnace splashes on the side of the electrode, shoulder 81 tends to scrape the slag from the electrode or alternatively, shifts the electrode slightly to allow the slag to pass through the opening.

By virtue of the arrangement of tie rods 87, which support lower seal ring 7, no appreciable force is exerted on the furnace roof as the electrode is lowered. Similarly, during upward movement of the electrode, even if the electrode jams in upper seal ring 9, any forces exerted on the seal ring, and correspondingly support ring 8 which prevents upward movement of the seal ring relative to the support ring, are resisted by tie rods 86, which as previously explained, are flexible, and permit the upper seal ring to lift the support ring, should the electrode jam in upper seal ring 9 as the electrode is lifted.

Lower seal ring 7, upper seal ring 9, and support ring 8 are formed from a high temperature resistant metal, such as stainless steel. As shown at FIG. 4, support ring 8 is fabricated by welding. Similarly, lower seal ring 7 and upper seal ring 9 can also be fabricated from preformed plates. Advantageously, top surface 20 of lower seal ring 7 is machined to provide a smooth seal surface, both the upper surface 42 and lower surface 84 of seal plate 40 are machined and are parallel with each other, and lower seal surface 72 or seal ring 9 is similarly machined to provide a smooth seal surface resistant to the escape of hot gases from the furnace when these components seat on each other, as shown at FIG. 4.

As will be noted with reference to FIG. 2, the extent of transverse movement of seal ring 9, relative to support ring 8, is limited by the inside surfaces of the several wall segments 43-46.

While a preferred embodiment of the improved furnace seal of this invention has been shown and described in detail, it is to be understood that numerous changes and modifications can be made without departing from the scope of this invention as stated herein and as defined in the appended claims.

What is claimed is:

1. In an electric furnace of the type in which an electrode extends through an opening in the furnace roof,

an electrode seal to seal the opening, said seal comprising a first seal ring adjacent said opening,

said ring presenting a first transverse seal surface; a second seal ring extending around the furnace electrode and of a diameter approximately the same as the electrode to provide a close clearance sliding fit therebetween said second ring having a second transverse sea] surface facing toward said first seal surface; an intermediate seal ring between said first and second seal rings and having oppositely facing seal surfaces, one of said surfaces engaging said first seal surface and the other of said surfaces engaging said second seal surface; and mounting means mounting said second seal ring for sliding movement along said one seal surface of said intermediate ring. 2. An electric furnace seal according to claim 1 wherein high temperature resistant packing is interposed between said second seal ring and the electrode. 3. An electric furnace seal according to claim 2 wherein said first seal ring is hollow and includes a cooling fluid passage; and said second seal ring is hollow and includes a cooling fluid passagev 4. An electric furnace seal according to claim 2 which further includes means carried by said second seal ring to guide the electrode through the ring. 5. An electric furnace seal according to claim 2 wherein said guide means includes an upwardly facing guide to guide the electrode during downward travel thereof, and a downwardly facing guide to guide the electrode during upward travel thereof. 6. An electric furnace seal according to claim 1 wherein said first and second rings each include a first arcuate segment, and a second arcuate segment secured to said first segment. 7. An electric furnace seal according to claim 1 wherein said first seal ring is mounted on the brick work of the furnace; said intermediate seal ring is seated on said first seal ring; said second seal ring is seated on said intermediate ring; and said mounting means is carried by said intermediate seal ring. 8. An electric furnace seal according to claim 7 wherein said mounting means mounts said second seal ring against separation from said one seal surface of said intermediate ring. 9. An electric furnace seal according to claim 8 wherein said mounting means includes a plurality of radially extending circumferentially spaced arms on said second seal ring, each of said arms having upwardly facing surfaces, and

a plurality of circumferentially extending plates secured to said intermediate ring, said plates presenting downwardly facing surfaces immediately adjacent said upwardly facing surfaces of said arms.

10. An electric furnace seal according to claim 9 wherein first support means at least partially supports said first seal ring independently of the furnace structure; and

second support means at least partially supports said intermediate ring independently of the furnace structure.

11. A seal arrangement to limit the loss of hot gases through an opening in a furnace roof through which an electrode extends, and is movable, comprising, in combination means defining an opening through which the electrode extends into the furnace, said opening being somewhat larger than the electrode;

means presenting an upwardly facing first seal surface surrounding the opening;

a seal ring extending around said electrode and having an opening therethrough of a dimension approximately that of the electrode, and a downwardly facing second seal surface engaging said first seal surface;

mounting means mounting said seal ring for radial movement relative to said first seal surface; and

support means supporting said means presenting said first seal surface independently of the roof of the furnace.

12. A seal arrangement to limit the loss of hot gases through an opening in a furnace roof through an opening in a furnace roof through which an electrode ex tends, and is movable, comprising, in combination means defining an opening through which the electrode extends into the furnace, said opening being somewhat larger than the electrode;

means presenting an upwardly facing first seal surface surrounding the opening;

a seal ring extending around said electrode and having an opening therethrough of a dimension approximately that of the electrode, and a downwardly facing second seal surface engaging said first seal surface;

mounting means mounting said seal ring for radial movement relative to said first seal surface;

a frusto-conical hat secured to said seal ring extending upwardly from the seal ring to define a space around the electrode; and

a high temperature resistant flexible packing filling said space around the electrode.

13. A seal assembly to seal an electrode movable through an opening in an electric melting furnace comprising, in combination means defining an opening through which the electrode extends into the furnace;

first seal means extending around said opening, said first seal means including inner wall means presenting a cylindrical opening,

and

a seal surface facing outwardly away from said opening;

second seal means including inner wall means defining a second opening of a diameter smaller than said cylindrical opening and only slightly larger than the diameter of said electrode, and

an inwardly facing seal surface engaging said outwardly facing seal surface;

mounting means mounting said second seal means for limited movement along said first seal means;

guide means on said second seal means to guide the electrode through said second opening;

packing retaining means on said seal means at a location axially outwardly of said inwardly facing seal surface; and

support means supporting said first seal means independently of the furnace brick work,

said support means including flexible support members allowing movement of said first seal means outwardly of the furnace.

14. A seal assembly to seal an electrode movable through an opening in an electric melting furnace comprising, in combination means defining an opening through which the electrode extends into the furnace;

first seal means extending around said opening, said first seal means including inner wall means presenting a cylindrical opening,

and

a seal surface facing outwardly away from said Opening;

second seal means including inner wall means defining a second opening of a diameter smaller than said cylindrical opening and only slightly larger than the diameter of said electrode, and

an inwardly facing seal surface engaging said outwardly facing seal surface;

mounting means mounting said second seal means for limited movement along said first seal means;

guide means on said second seal means to guide the electrode through said second opening;

packing retaining means on said second seal means at a location axially outwardly of said inwardly facing seal surface; and wherein:

said first seal means includes a support ring having an inwardly directed seal surface, and

an outwardly directed seal surface;

third seal means is mounted between said support ring and said furnace and presents a seal surface engaging said inwardly directed seal surface of said support ring; and

said inwardly facing seal surface of said second seal means engages said outwardly facing surface of said support ring.

15. A seal assembly according to claim 14 wherein said support ring includes means connecting the second seal means to the support ring for transverse movement thereon, but against axial separation; and support means supporting said support ring independently of the furnace brick work for limited movement axially away from the furnace.

16. A seal assembly to seal an electrode movable through an opening in an electric melting furnace comprising, in combination means defining an opening through which the electrode extends into the furnace;

first seal means extending around said opening, said first seal means including inner wall means presenting a first opening larger than the electrode, and

a transverse seal surface facing outwardly away from said opening;

second means including inner wall means defining an axially short second opening of a diameter smaller than said first opening and only slightly larger than the diameter of the electrode, whereby a clearance space is provided to permit tilting of the electrode relative to the axis of said second opening, and

an inwardly facing transverse seal surface engaging said outwardly facing seal surface;

mounting means mounting said second seal means for transverse movement along said first seal means guide means on said second seal means to guide the electrode through said second opening; and

a high temperature resistant packing on said second seal means at a location axially outwardly of said inwardly facing sea] surface, said packing permitting tilting of said electrode at said axially short opening.

17. A seal arrangement according to claim 16 wherein said guide means on said second seal means includes means presenting a slanting guide surface at one end of said second opening, and

means presenting a slanting guide surface at the other end of said second opening.

18. A seal arrangement according to claim 16 45 wherein said second seal means includes a plurality of arms rigid with said inner wall means of the second seal means and projecting transversely thereof; and said mounting means includes a ring rigid with said first seal means and extending around said second seal means, said ring having slots therein with closed ends to receive said arms and restrain said second seal means against axial movement. 

1. In an electric furnace of the type in which an electrode extends through an opening in the furnace roof, an electrode seal to seal the opening, said seal comprising a first seal ring adjacent said opening, said ring presenting a first transverse seal surface; a second seal ring extending around the furnace electrode and of a diameter approximately the same as the electrode to provide a close clearance sliding fit therebetween said second ring having a second transverse seal surface facing toward said first seal surface; an intermediate seal ring between said first and second seal rings and having oppositely facing seal surfaces, one of said surfaces engaging said first seal surface and the other of said surfaces engaging said second seal surface; and mounting means mounting said second seal ring for sliding movement along said one seal surface of said intermediate ring.
 2. An electric furnace seal according to claim 1 wherein high temperature resistant packing is interposed between said second seal ring and the electrode.
 3. An electric furnace seal according to claim 2 wherein said first seal ring is hollow and includes a cooling fluid passage; and said second seal ring is hollow and includes a cooling fluid passage.
 4. An electric furnace seal according to claim 2 which further includes means carried by said second seal ring to guide the electrode through the ring.
 5. An electric furnace seal according to claim 2 wherein said guide means includes an upwardly facing guide to guide the electrode during downward travel thereof, and a downwardly facing guide to guide the electrode during upward travel thereof.
 6. An electric furnace seal according to claim 1 wherein said first and second rings each include a first arcuate segment, and a second arcuate segment secured to said first segment.
 7. An electric furnace seal according to claim 1 wherein said first seal ring is mounted on the brick work of the furnace; said intermediate seal ring is seated on said first seal ring; said second seal ring is seated on said intermediate ring; and said mounting means is carried by said intermediate seal ring.
 8. An electric furnace seal according to claim 7 wherein said mounting means mounts said second seal ring against separation from said one seal surface of said intermediate ring.
 9. An electric furnace seal according to claim 8 wherein said mounting means includes a plurality of radially extending circumferentially spaced arms on said second seal ring, each of said arms having upwardly facing surfaces, and a plurality of circumferentially extending plates secured to said intermediate ring, said plates presenting downwardly facing surfaces immediately adjacent said upwardly facing surfaces of said arms.
 10. An electric furnace seal according to claim 9 wherein first support means at least partially supports said first seal ring independently of the furnace structure; and second support means at least partially supports said intermediate ring independently of the furnace structure.
 11. A seal arrangement to limit the loss of hot gases through an opening in a furnace roof through which an electrode extends, and is movable, comprising, in combination means defining an opening through which the electrode extends into the furnace, said opening being somewhat larger than the electrode; means presenting an upwardly facIng first seal surface surrounding the opening; a seal ring extending around said electrode and having an opening therethrough of a dimension approximately that of the electrode, and a downwardly facing second seal surface engaging said first seal surface; mounting means mounting said seal ring for radial movement relative to said first seal surface; and support means supporting said means presenting said first seal surface independently of the roof of the furnace.
 12. A seal arrangement to limit the loss of hot gases through an opening in a furnace roof through an opening in a furnace roof through which an electrode extends, and is movable, comprising, in combination means defining an opening through which the electrode extends into the furnace, said opening being somewhat larger than the electrode; means presenting an upwardly facing first seal surface surrounding the opening; a seal ring extending around said electrode and having an opening therethrough of a dimension approximately that of the electrode, and a downwardly facing second seal surface engaging said first seal surface; mounting means mounting said seal ring for radial movement relative to said first seal surface; a frusto-conical hat secured to said seal ring extending upwardly from the seal ring to define a space around the electrode; and a high temperature resistant flexible packing filling said space around the electrode.
 13. A seal assembly to seal an electrode movable through an opening in an electric melting furnace comprising, in combination means defining an opening through which the electrode extends into the furnace; first seal means extending around said opening, said first seal means including inner wall means presenting a cylindrical opening, and a seal surface facing outwardly away from said opening; second seal means including inner wall means defining a second opening of a diameter smaller than said cylindrical opening and only slightly larger than the diameter of said electrode, and an inwardly facing seal surface engaging said outwardly facing seal surface; mounting means mounting said second seal means for limited movement along said first seal means; guide means on said second seal means to guide the electrode through said second opening; packing retaining means on said seal means at a location axially outwardly of said inwardly facing seal surface; and support means supporting said first seal means independently of the furnace brick work, said support means including flexible support members allowing movement of said first seal means outwardly of the furnace.
 14. A seal assembly to seal an electrode movable through an opening in an electric melting furnace comprising, in combination means defining an opening through which the electrode extends into the furnace; first seal means extending around said opening, said first seal means including inner wall means presenting a cylindrical opening, and a seal surface facing outwardly away from said opening; second seal means including inner wall means defining a second opening of a diameter smaller than said cylindrical opening and only slightly larger than the diameter of said electrode, and an inwardly facing seal surface engaging said outwardly facing seal surface; mounting means mounting said second seal means for limited movement along said first seal means; guide means on said second seal means to guide the electrode through said second opening; packing retaining means on said second seal means at a location axially outwardly of said inwardly facing seal surface; and wherein: said first seal means includes a support ring having an inwardly directed seal surface, and an outwardly directed seal surface; third seal means is mounted between said support ring and said furnace and presents a seal surface engaging said inwardly directed seal surface Of said support ring; and said inwardly facing seal surface of said second seal means engages said outwardly facing surface of said support ring.
 15. A seal assembly according to claim 14 wherein said support ring includes means connecting the second seal means to the support ring for transverse movement thereon, but against axial separation; and support means supporting said support ring independently of the furnace brick work for limited movement axially away from the furnace.
 16. A seal assembly to seal an electrode movable through an opening in an electric melting furnace comprising, in combination means defining an opening through which the electrode extends into the furnace; first seal means extending around said opening, said first seal means including inner wall means presenting a first opening larger than the electrode, and a transverse seal surface facing outwardly away from said opening; second means including inner wall means defining an axially short second opening of a diameter smaller than said first opening and only slightly larger than the diameter of the electrode, whereby a clearance space is provided to permit tilting of the electrode relative to the axis of said second opening, and an inwardly facing transverse seal surface engaging said outwardly facing seal surface; mounting means mounting said second seal means for transverse movement along said first seal means guide means on said second seal means to guide the electrode through said second opening; and a high temperature resistant packing on said second seal means at a location axially outwardly of said inwardly facing seal surface, said packing permitting tilting of said electrode at said axially short opening.
 17. A seal arrangement according to claim 16 wherein said guide means on said second seal means includes means presenting a slanting guide surface at one end of said second opening, and means presenting a slanting guide surface at the other end of said second opening.
 18. A seal arrangement according to claim 16 wherein said second seal means includes a plurality of arms rigid with said inner wall means of the second seal means and projecting transversely thereof; and said mounting means includes a ring rigid with said first seal means and extending around said second seal means, said ring having slots therein with closed ends to receive said arms and restrain said second seal means against axial movement. 